1. Field of the Invention
This invention relates to haze inhibited lubricating oil compositions having an improved viscosity index resulting from the presence of a hydrocarbon polymeric viscosity index improver as well as to the haze-inhibited additive concentrates by means of which said lubricating oil compositions are formulated. In particular, this invention is directed to haze-free lubricating oil compositions and additive packages used in formulating them, and methods for their preparation, containing hydrocarbon polymers, particularly ethylene-propylene copolymer viscosity index improvers. In its preferred form, the invention is directed to hydrocarbon polymers produced by processes resulting in oil insoluble metal containing contaminants which normally impart haze to the oil composition and a haze inhibiting amount of an oil soluble compound which chelates and solubilizes said metal containing haze component.
The problem of haze in oil solutions due to metal contaminants resulting from the preparation of polymers for use as viscosity index improvers is discussed in U.S. Pat. No. 4,069,162 which teaches the addition of oil soluble strong acids, e.g. an alkaryl sulfonic acid, to inhibit such haze.
U.S. Patent application Ser. No. 110,004 now U.S. Pat. No. 4,282,108 to Harold E. Deen et al teaches various oxazolidines resulting from the reaction of cyclic ketone and amino alcohol as oil additives and as chelating agents for functional fluids, including lubricating oils and synthetic lubricants.